To meet the increasing demands of wide-bandwidth and high speed mobile access, the Third Generation Partnership Projects (3GPP) adopts Long-Term Evolution advance (LTE-Advanced) standard.
For the Long-Term Evolution (LTE), the LTE-Advanced retains the core of LTE in its evolution, and on this basis, adopts a series of technologies to expand the frequency and spatial domain, which achieves goals like improving spectrum efficiency, increasing system capacity, etc.
The wireless Relay Technology is one of the LTE-Advanced technologies, which aims at extending cell coverage, reducing dead-ends area in communication, balancing loads, transferring services in a hot-spot area and saving transmit power of a user equipment (UE).
As shown in FIG. 1, a Relay Node (RN) provides functions and services similar to those of a common evolved Node B (eNB) for the UE which accesses to its cell, and also accesses an eNB which services it through a wireless interface in a way similar with that of a common UE.
An eNB that services the RN is referred to as a Donor eNB (DeNB). The DeNB connects with a Mobility Management Entity (MME), wherein a Serving Gateway (S-GW) function and a Packet Data Network Gateway (P-GW) function, as well as a Relay Gateway (GW) function are set in the DeNB, as shown in FIG. 2.
When the RN accesses to the DeNB, the MME will choose the local S-GW and P-GW located in the DeNB for the RN. The S-GW is responsible for transmitting, forwarding, and routing data information between the base station and the P-GW, and providing cache for downlink data packets.
The P-GW is an anchor for a data bearer, which is responsible for forwarding, analysis, lawful interception of the data packet, charging based on the services, and Quality of Service (QoS) control.
The Relay GW which acts as an S1/X2 proxy function, is responsible for processing S1/X2 signallings related to the UE, distinguishing signallings for different UEs, and processing messages correctly. For example, in a fixed relay scenario, an X2 proxy function refers to that there is an X2 interface between the DeNB and the RN1, and there is an X2 interface between the DeNB and neighboring eNB(s) or other RN(s). When the DeNB (Relay GW) has received an X2 message of the RN1, it decides to transfer a related X2 message to which neighboring eNB (s) or RN according to cell information in the X2 message, if the message carries a UE application layer protocol identifier, the DeNB allocates a new UE application layer protocol identifier to the UE, or uses the application layer protocol identifier that has already been allocated to the UE to replace the UE application layer protocol identifier that previously carried in the message, and carries it as the UE application layer identifier allocated by the DeNB in the X2 message sent to other neighboring base stations. When the DeNB (Relay GW) has received an X2 message from other eNB (s) or other RN, it decides whether to send the related X2 message to the RN1 according to the cell information in the X2 message. If the message carries the UE application layer protocol identifier, the DeNB allocates a new UE application layer protocol identifier to the UE, or uses the application layer protocol identifier that has already been allocated to the UE to replace the UE application layer protocol identifier that is previously carried in the message, and carries it as the UE application layer protocol identifier allocated by the DeNB in an X2 message sent to the RN1.
For example, if the received X2 message indicates that the target cell is the RN1, a corresponding X2 message is sent to the RN1.
For example, if the received X2 message is a base station configuration updating message, the base station configuration updating message is sent to the RN accordingly.
By means of the X2 proxy, the information transmission between the RN and other neighboring eNB (s) or RN can be achieved. Wherein, the S1/X2 signal between the RN and the DeNB (Relay GW) is loaded wirelessly by RN, and is transmitted through RN SGW/PGW routing and transferring.
With the large-scale construction and putting into operation of the high speed railway, the demand of communication on the train is increasing. Currently, the practical speed of the high speed railway has reached to 350 km/h. Influenced by Doppler shift, frequent cell handover, large penetration loss of the high-speed rail compartment, coverage of a base station in a related network is difficult to meet the demand of the high-speed rail communication quality. As a result, the industry proposes deploying Relay Nodes on the high-speed rail, which are called mobile relays. As shown in FIG. 1, it is to make the users in a train of the high-speed rail (e.g. UE1 and UE2) directly communicate with a relatively static RN, while the RN can perform handover between different DeNBs in the process of the high-speed rail moving, thereby a large number of users in the compartment are presented from performing handover at the same time, thus ensuring the communication quality between the UE and the RN. In addition, by strengthening the backbone connection between the mobile RN and the DeNB, the above problems existing in the high-speed railway can be well solved.
As for a mobile relay scenario, at present many kinds of structures have been put forward. Among them, Alt2 (without relocation) reuses the structure of the fixed relay, that is, an S-GW function, a P-GW function, and a Relay GW are set in the DeNB. When a Mobile Relay (MR) accesses to an initial DeNB, it can reuse a proxy (X2 proxy) between two nodes to achieve X2 message transmission between the MR and other eNB(s).
During the process of implementing embodiments of the present document, the inventor of the present application finds that in related technologies, when the MR moves with the train and is far away from the initial DeNB, and after handing over to other DeNB, the Relay GW/RN S/PGW of the MR still resides in the initial DeNB. Since the initial DeNB is far away from the current MR, an X2 interface may not exist between the MR and the neighboring eNB(s), so the X2 proxy cannot work between the MR and these eNB(s). At present, the Relay Node and the DeNB only maintain one X2 proxy, there is no method for a plurality of X2 proxies, and no method for maintaining two or more X2 proxies synchronously.
In a Home evolved Node B (HeNB) scenario, when an HeNB exchanges information with a neighboring eNB or an HeNB through an X2 proxy, the above similar problems may occur, which affects the X2 information transmission between the HeNB and other eNB or HeNB. In the HeNB scenario, the X2 proxy can also be called as an X2 GateWay, which has a function similar with that of the X2 proxy in the mobile relay scenario.